The overhaul of internal combustion engines is an expensive, difficult and time-consuming process. Virtually all internal combustion engines include valves which are operated against spring pressure, and there are at least two valves for each cylinder. Thus, in order to disassemble and reassemble the engine, and specifically the cylinder head, means must be provided to manipulate the valves so that the springs can be removed or attached. These springs are fairly stiff and require a considerable amount of force to be applied to the valve, typically by way of a specialized clamp. This clamp spans a portion of the cylinder head so that it reaches both the valve face and the spring, simultaneously lifting the valve and compressing the spring. Since engines are configured in many different ways, valve locations can vary so that a clamp is required for each type of engine to be serviced, and different valves within a single engine introduce further variables and requirements due to the shape of the engine. This can result in considerable expense to a mechanic to have one or more clamp for each valve arrangement. Further, if the mechanic only has one clamp for a particular valve arrangement, the valves must be disassembled/reassembled serially, making the procedure tedious and time consuming. Thus, duplicate tools may be required. The added tool and labor costs contribute to the time and expense involved in an engine overhaul.
In co-pending applications Ser. Nos. 07/855,098 and 07/915,018, the present inventor disclosed a method and apparatus for facilitating the assembly/disassembly of engine valves. Application Ser. No. 07/855,098 described the procedure for introducing high pressure gas into the combustion chamber of the cylinder head to force the valves outward, compressing the valve springs, to facilitate removal of the key bolt, the small, two-piece ring which wedges into the groove in the valve stem. In the invention of application Ser. No. 07/915,018, the inventor utilized a deformable bladder which expands upon the introduction of a fluid, typically air, to fill the combustion chambers and force the valves outward.
Another step in the disassembly/re-assembly of engine valves is the actual removal/replacement of the key bolts, or locks, which retain the springs on the valve stems. A number of methods are used to accomplish this. In many garages and shops, drill presses are used to supply downward pressure on the upper cup which retains the spring to free the key bolt. The popularity of this practice is primarily due to the fact that many shops have drill presses, and may not have other more appropriate tools. This improvisation, however, puts the valves, and possibly the drill press, at risk, since the work area of the drill press is not intended to handle cylinder heads. Another technique involves striking the end of the valve stem or the upper cup with an inertia hammer. Besides being hazardous to the valves, and somewhat "inexact", there is a risk in these procedures of losing the key bolt after it comes loose.
Further complications are experienced during re-assembly of the valves and springs into the cylinder head. First, the tiny key bolt pieces can be dropped while trying to insert them into the retaining ring. The valves can fall out of the valve guides while attempting to reassemble them since there is nothing to hold them in the position to permit access to the valve stem. Also, careful centering of the valve stems within the cam bucket bore is necessary to avoid damage to the bore's inner wall.